Earthlike Mars? |
Earthlike Mars? |
Apr 1 2009, 02:28 AM
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#1
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Member Group: Members Posts: 233 Joined: 21-April 05 Member No.: 328 |
All, I know this isn't the right place for this post, but I've looked around and can't find an appropriate, current UMSF forum (Doug, perhaps you could give me some guidance on establishing such) -- so here goes: I think a [the] new paradigm for Martian geology is rapidly coalescing, namely, that Mars is very much like the Earth in terms of the preponderance of water -- except that it is all frozen, and covered under a thin layer of dust/regolith! See, for example, this article:
http://www.skyandtelescope.com/news/41995902.html Hence the "seepages" found in crater walls; hence the evidence of catastophic flooding -- the result of volcanism melting huge pockets of ice. And I am going to add my own wrinkle (probably not original): that the differentiation of Mars into a rougher southern hemisphere and smoother northern hemsphere represents something like Earth's Pangea stage, ie, the northern hemisphere is a vast frozen sea covered with a thin layer of ice. |
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May 24 2009, 10:36 PM
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#2
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Member Group: Members Posts: 233 Joined: 21-April 05 Member No.: 328 |
Whoa! Marsbug and Doc, thanks for alerting me to the fact that the question of an Oceanus Borealis is entangled (as of course it must be) with the heated debates regarding basal surge versus water-based processes. I have been involved in that frustrating loop myself when I, along with Dvandorn and many others, remarked on the incredible layering of Meridiani. So part of my goal with this thread is to approach things from a different, simplistic angle: was there (or is there still, in frozen form) a vast ocean in the northern basin? When Phoenix landed on a sheet of ice, and when meteorites at widely spaced intervals are turning up ice, the presence of such seems likely to me. Interestingly, even Dburt advances the possibility of a northern ocean, in post #36 from the thread which Marsbug turned me on to, "Welcome Professor Brine Splat":
"Large amounts of water apparently survived in the subsurface, however, as both ice and (probably) deep brine (as evidenced by occasional catastrophic releases to outflow channels that possibly formed ephemeral seas in the northern lowlands)." And I will now succumb to the temptation to use an emoticon: |
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May 25 2009, 07:26 AM
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#3
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Member Group: Members Posts: 384 Joined: 4-January 07 Member No.: 1555 |
Thanks for the emoticon, Glenn, but do you have a question? If Mars has almost always been rather cold and icy compared to Earth, owing to a much greater distance from the Sun and a paucity of atmosphere, this does not prohibit temporary surface warming (i.e., for perhaps several thousands or hundreds of thousands of years) owing to major meteorite impacts or groups of impacts, nor does it prohibit liquid water from existing on present-day Mars as concentrated brines or as very ephemeral snowmelt in low elevations containing dark (easily heated) basaltic rocks or dust. It also does not exclude local warming and brine beakouts near volcanic centers, although these centers seem to have rapidly declined in number after the end of major meteorite bombardment (the so-called Late Heavy Bombardment or LHB). Given how ice-rich Mars seems to be, soon-to-be-frozen-over lakes filling impact basins or even a temporary sea filling the Northern Lowlands could easily form following a really major impact event or series of events.
That said, 5 years of two rovers wandering across the present-day surface of Mars has as yet revealed no direct geological evidence of standing or flowing liquid water (such as a single shale bed or single pebbly stream channel) in the bedded rocks that make up both rover sites, although various interpretations have been made, entirely on the basis of preexisting expectations and putative terrestrial analogs. All the exposed fine layering at both rover sites is consistently cross-bedded, generally at low angles, and both sites contain enigmatic concentrations of generally unclumped tiny spherules (in distinct layers) and of acid sulfate salts. One site, in which most of the layering is rather coarse (breccias with abunandant lava fragments), contains a distinct horizon with silica-rich fragments, such as might originally have been produced in a boiling (easy to do on low pressure Mars) hot spring related to an impact crater or volcano. AFAIK, both sites contain abundant evidence of meteorite impacts, including evidence of very recent impacts and of actual fragments of meteorites on the surface, but neither site contains locatable volcanic vents. I don't care to discuss further my own rather obvious and by now way over-explained (to most readers) interpretations of these highly interesting and valuable scientific observations. Occam's Razor, the Rosenthal (experimenter expectation) effect, and all that. Nuff said, although new contrary observations and interpretations remain highly welcome (send me a private message if you wish). -- HDP Don |
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